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					Atomic Structure
You already know something about atoms

   Atoms are made of three subatomic particles.
   Those subatomic particles are called the
    protons, neutrons and electrons.
   The center of the atom is called the nucleus.
   The electrons orbit the atom in distinct energy
    levels
Now, let’s see what you know about the
subatomic particles. Which subatomic
particle has no charge and a mass of 1
a.m.u.?
1.   proton
                      25%   25%   25%   25%
2.   neutron
3.   valance
4.   electron



                       1     2     3     4
   Which subatomic particle has a
positive charge and a mass of 1 a.m.u.?
                     25%   25%   25%   25%
1.   proton
2.   neutron
3.   valance
4.   electron



                      1     2     3     4
     Which subatomic particle has a -1
      charge and a mass of about 0 ?


1.   proton
                       25%   25%   25%   25%
2.   neutron
3.   valance
4.   electron



                        1     2     3     4
     What is the term for electrons in the
           outermost energy level?
                         25%   25%   25%   25%

1.    proton
2.    neutron
3.    valance
4.    electron



                          1     2     3     4
          History of the Atom
460 BC   Democritus develops the idea of atoms

                       Democritus pounded up
                        materials in his mortar
                        and pestle until
                        reduced to smaller
                        and smaller particles,
                        which he called
                        ATOMA (Greek for
                        indivisible)
During that time, the most famous/popular
thinker was Aristotle. Aristotle believed
that all substances were made up of
combinations of Air, Earth, Fire and
Water. Since Aristotle was more popular
than Democritus, the idea of the four
elements was used for almost another 2000
years ! And the atoma was ignored!
1808   John Dalton

         Dalton suggested
          that all matter was
          made up of tiny
          spheres that
          bounce off of each
          other with perfect
          elasticity. He called
          them ATOMS.
1808   John Dalton

         Dalton suggested
          that all matter was
          made up of tiny
          spheres that
          bounce off of each
          other with perfect
          elasticity. He called
          them ATOMS.
J. J. Thompson
1898   Joseph J. Thompson
             Thompson was an
              English physicist
              who found that
              atoms could
              sometimes eject a
              far smaller
              negative particle
              which he called an
              ELECTRON.
1904

Six years later, J J Thompson develops
 the idea that an atom was made up of
 electrons scattered unevenly within a
 sphere, surrounded by a soup of
 positive charge to balance the charge
 of the atom. This description is known
 as the PLUM PUDDING MODEL.
1910   Ernest Rutherford
            Rutherford is famous for his
              gold foil experiment. Gold is
              extremely ductile, meaning
              it can be stretched
              extremely thin. His research
              group fired helium nuclei at
              a piece of gold foil only a
              few atoms thick. Most of the
              positively charge nuclei
              passed through. Many were
              unexpectedly deflected, and
              a few bounced straight
              back.
    Rutherford’s gold foil experiment
The new evidence lead
  the group to propose a
  central, positively
  charged nucleus. The
  nucleus was
  surrounded by the
  negatively charged
  electrons, held in place
  by electrical attraction.
  In his model, the
  electrons were
  randomly placed.
1913   Niels Bohr

        A student of Rutherford’s,
          Bohr suggested that
          the electrons moved in
          orbits like planets
          circling the sun. And,
          he proposed, each orbit
          could only contain a set
          number of electrons.
Bohr Model of Helium

          Notice the four balls at the
            center of the atom –
            two positively charged
            protons (red) and two
            neutral neutrons
            (green). The much
            smaller negatively
            charged electrons orbit
            the nucleus at a single
            energy level.
The Bohr Model of Nitrogen

             How can one tell this is a
               model of nitrogen?
Which element is represented by this Bohr
model?


                      25%   25%   25%   25%




1.   hydrogen
2.   lithium
3.   carbon
4.   neon
                       1     2     3     4
Which element is represented by this Bohr
model?


                      25%   25%   25%   25%




1.   hydrogen
2.   lithium
3.   carbon
4.   neon
                       1     2     3     4
  Both of these electron orbitals are full.
The first shell can hold only two electrons.
 The second energy level can hold eight.
            Atomic Structure
Subatomic        Charge         Mass
 particle

 Proton            +1          1 a.m.u.


 Neutron        No charge      1 a.m.u.


 Electron          -1          About 0
The element symbol can include the atomic
number (red) and the atomic mass (blue).
The atomic mass is equal to the number of
  protons plus the number of neutrons.


   4
   2   He
                 Atomic Structure

   First energy level      →       2 electrons

   Second energy level             →      8 electrons

   Third energy level       →      8 electrons*

* The third energy level actually holds 18, but the level fills
  with 8 first.
           Atomic Structure

Two common ways to represent the atomic
   structure of an element or compound:

         Electron configuration

              Bohr model
              Electron Configuration

Nitrogen has 7 electrons, so where will they be?
  The inner orbital fills first, so 2 electrons go
  there. That leaves 5 to go in the second.

So the electron configuration of nitrogen can be
  written:
   14
    7   N
        2,5
What element has the electron
configuration 2,4 ?
                      25%   25%   25%   25%



1.   hydrogen
2.   carbon
3.   neon
4.   silicon



                       1     2     3     4
What element has the electron
configuration 2,8 ?
                      25%   25%   25%   25%



1.   hydrogen
2.   carbon
3.   neon
4.   silicon



                       1     2     3     4
What element has the electron
configuration 2,8,4 ?
                      25%   25%   25%   25%



1.   hydrogen
2.   carbon
3.   neon
4.   silicon



                       1     2     3     4
What element is represented by this Bohr
model?

                       25%   25%   25%   25%




1.   hydrogen
2.   carbon
3.   neon
4.   silicon
                       1      2     3      4
                   Summary

   The atomic number of an atom = number of
    protons in the nucleus
   The atomic mass of an atom = number of
    protons + number of neutrons (in the
    nucleus)
   The number of protons = number of electrons
   Electrons orbit the nucleus in energy levels
   Each energy level can only hold a set number
    of electrons
Let’s see what you remember. Who is
credited with first proposing an atom?
                         17%   17%   17%   17%   17%   17%

1.   Aristotle
2.   Democritus
3.   John Dalton
4.   J.J. Thompson
5.   Ernest Rutherford
6.   Neils Bohr

                         1     2      3     4     5     6
Who is credited with first proposing that
electrons are in fixed energy levels?
                         17%   17%   17%   17%   17%   17%

1.   Aristotle
2.   Democritus
3.   John Dalton
4.   J.J. Thompson
5.   Ernest Rutherford
6.   Neils Bohr

                         1     2      3     4     5     6
Who is credited with plum pudding model of
the atom?
                         17%   17%   17%   17%   17%   17%

1.   Aristotle
2.   Democritus
3.   John Dalton
4.   J.J. Thompson
5.   Ernest Rutherford
6.   Neils Bohr

                         1     2      3     4     5     6
Who is credited with the center of an atom
has a positively charged center with his gold
foil experiment?
                         17%   17%   17%   17%   17%   17%
1.   Aristotle
2.   Democritus
3.   John Dalton
4.   J.J. Thompson
5.   Ernest Rutherford
6.   Neils Bohr

                         1     2      3     4     5     6
What does the blue “4” represent in the
expression?
                     4
                     2   He
                          25%   25%   25%   25%


1.   Color of the atom
2.   Number of neutrons
3.   Atomic number
4.   Atomic mass


                          1      2     3     4
What does the red “2” represent in the
expression?
                     4
                     2   He
                          25%   25%   25%   25%


1.   Color of the atom
2.   Number of neutrons
3.   Atomic number
4.   Atomic mass


                          1      2     3     4
Which subatomic particle has a mass
of 1 a.m.u. and no charge?
                    25%   25%   25%   25%




1.   proton
2.   neutron
3.   orbital
4.   electron


                     1     2     3     4
Which subatomic particle has almost
no mass and a charge of - 1?
                    25%   25%   25%   25%




1.   proton
2.   neutron
3.   orbital
4.   electron


                     1     2     3     4
Which subatomic particle has a mass
of 1 a.m.u. and a charge of + 1?
                    25%   25%   25%   25%




1.   proton
2.   neutron
3.   orbital
4.   electron


                     1     2     3     4
In which part of an atom are the
protons found?
                       25%   25%   25%   25%




1.   nucleus
2.   energy levels
3.   orbitals
4.   electron shells


                       1      2     3     4
In which part of an atom are the
neutrons found?
                       25%   25%   25%   25%




1.   nucleus
2.   energy levels
3.   orbitals
4.   electron shells


                       1      2     3     4
How many electrons can the first
energy level hold?
                    25%   25%   25%   25%




1.   one
2.   two
3.   six
4.   eight


                     1     2     3     4
How many electrons can the second
energy level hold?
                   25%   25%   25%   25%




1.   one
2.   two
3.   six
4.   eight


                    1     2     3     4
What element is represented by the
following Bohr model?

                      25%   25%   25%    25%




1.   hydrogen
2.   helium
3.   carbon
4.   oxygen
                       1     2       3    4
What element is represented by the
electron configuration 2,4?
                      17%   17%   17%   17%   17%   17%

1.   hydrogen
2.   helium
3.   carbon
4.   oxygen
5.   sililcon
6.   calcium

                      1     2      3     4     5     6
What element is represented by the
electron configuration 2,6?
                      17%   17%   17%   17%   17%   17%

1.   hydrogen
2.   helium
3.   carbon
4.   oxygen
5.   sililcon
6.   calcium

                      1     2      3     4     5     6
What element is represented by the
electron configuration 2,8,8,2?
                      17%   17%   17%   17%   17%   17%

1.   hydrogen
2.   helium
3.   carbon
4.   oxygen
5.   sililcon
6.   calcium

                      1     2      3     4     5     6
                               GOOD JOB

                       Thanks for participating.




Credit goes to S. Morris for slide information.

				
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